How to map keys in Blender 2.80?
You can change shortcuts in the Keymap section of the Blender Preferences. Just open up the preferences and search for either the name of the function you want to remap, which in this case is 'view selected' and all the bindings for it will appear. You then simply click on the current shortcut and Blender will ask you to press the key you want to change it to.



Note that in Blender 2.80 you can also bind keys by right-clicking on buttons or options in menus and selecting 'Assign Shortcut'. Since the frame selected function doesn't appear on any menus, it must be assigned in the preferences.